Main Menu
Star Resources
With A
6: Overview
Main Menu > 6: Space Weather > Sun-Earth Connection > Plasma Clouds Around Earth 
Plasma Clouds Around Earth

Ring current shown around the Earth
Ring current shown around the Earth demonstrated by images from IMAGE/HENA instruments. The lines show the magnetic field as viewed from nearly above the North Pole.
The environment of Earth in space is a complicated stew of energetic particles such as protons and electrons. Space scientists have discovered, however, that it is possible to discern three distinct ingredients to this stew. Like salt and pepper mixed together, each system of particles has its own unique properties. The densities of these components are so low that the particles only occasionally collide with one another as they travel around Earth at speeds of thousands of kilometers per hour or more. One of these components, the Van Allen belts, is a well-known landmark of near-Earth space discovered at the dawn of the Space Age. 

Van Allen Belts
Encircling the equatorial region of the Earth, and extending to latitudes nearly as far as the Arctic Circle, the Van Allen belts form two, nested donuts of particles. The inner belt contains 10 million-volt, high-energy protons (the stripped nuclei of hydrogen atoms), and is located between 700 kilometers and 12,000 kilometers from the Earth's surface. The outer belt contains mostly electrons with energies higher than one million volts, located between 25,000 and 40,000 kilometers from the Earth’s surface. Both belts are severe radiation hazards for astronauts, which is why the orbits of the International Space Station and typical Space Shuttle missions are well below the inner edges of these belts. The Van Allen belts are always present in space, like fixed coral reefs in the ocean, which must be avoided at all times.

The location of the inner and outer Van Allen radiation belts.
The Plasmasphere
A second population of particles, the plasmasphere, consists of low-energy particles with energies of a few tens of volts. Unlike the Space Shuttle which orbits Earth once every 90 minutes under the influence of gravity, plasmasphere particles are not under the influence of gravity at all. Earth's magnetic field is so strong that the plasmasphere particles are actually pulled along with Earth's 24-hour rotation at a much slower speed than the Space Shuttle. Like the Van Allen belts, the plasmasphere is a permanent feature of Earth's environment, though it is not a health hazard for astronauts.

The Ring Current
The third component of near-Earth space is the ring current which overlaps both the Van Allen belts and the plasmasphere from 8,000 to 30,000 kilometers from Earth. Ring current particles carry energies of several thousand volts, but unlike Saturn's rings, they do not flow in a complete ring around Earth. It is more prominent on the night time side of Earth, and it is at its strongest, carrying the most particles, during severe solar storm events which shake Earth's magnetosphere. This current of particles carries enough energy to actually change the strength of Earth's magnetic field even at ground level, especially in the equatorial regions. Although Van Allen belt particles are probably captured from the solar wind, and plasmasphere particles probably come from the upper atmosphere and ionosphere, the origin of the ring current particles is something of a scientific mystery. Scientists don't fully understand where they come from, or how they get energized to such high voltages within the magnetosphere.

globe icon Find out more about the Sun-Earth Connection at the Sun-Earth Connection Education Forum Web site.

Text adapted from the Sun-Earth Connection Tutorial courtesy of NASA, originally written by Dr. Sten Odenwald. Images and videos courtesy of NASA unless otherwised noted.

Related to chapter 6 in the print guide.
Related Materials

Visit other pages in this section that focus on aspects of the Sun-Earth Connection.

The Solar Interior
Solar Cycle
Solar Flares
The Solar Wind
Plasma Clouds
Glossary Terms

Click for the definitions of the following words that are used on this page: (Definitions appear in a pop-up window.)

coronal mass ejection
geomagnetic field
geomagnetic storm
radiation belts
solar cycle
solar maximum
solar minimum
solar wind

View the full, printable version of the glossary.

Top of Page
Last Page Next Page
Main Menu | Resources | 6: Overview

©2002 UC Regents